Nationwide over one million or 6-9%1 of all children suffer from dysphonia. Dysphonia can be detrimental to children both psychologically and academically, hence early identification and restoration of optimal vocal health is critical. Direct visualization of vocal fold vibratory patterns is fundamental to appropriate diagnosis and treatment of vocal fold pathology. Objective assessments of vocal fold physiology are non-existent in the field of pediatric voice care, leading to delayed diagnosis and deferred development of effective treatments. The long term goal of the proposed research is to improve treatment outcomes and early identification in children with hoarseness by establishing age appropriate quantitative measurements of immature vocal fold function that contribute to voice disorders. To accomplish this goal, it is necessary to quantify vocal fold vibrations resulting from differences in the multilayered vocal fold structure of children compared with adults. Most voice problems in children are thought to be caused by mechanical trauma to the vocal folds manifested as high impact stress, leading to the development of vocal nodules. The specific goal of this project is to identify the impact of growth and development of the layered structure of the vocal folds on vocal physiology and the relationship of these factors to the development of vocal fold nodules in children. This research proposes 1 milestone-driven aim and 2 hypotheses-driven aims. Therefore, the specific aims of this application are: 1) to optimize a 2-point laser projection system developed in our laboratory for precision and to compute expected measurement variability to fully translate use of this system to children, 2) to quantify the relationship between short vocal fold length and increased vibratory amplitude during the developmental process in children with and without nodules, and 3) to quantify spatiotemporal features of vocal fold impact stress in children as a function of age and pathology. A total of 80 children will be recruited to participate (ages: 5-12), 40 with and 40 without nodules. Forty adults (21-45 years) will be recruited to obtain the developmental end point for maturation of vibratory motion because adults have a well-defined layered structure of the vocal folds. The following spatiotemporal features of vocal fold vibrations will be measured using a novel 2-point pediatric laser high speed digital imaging system to identify impact stress: mid membranous amplitude-to-length ratio, peak vocal fold acceleration(mm/sec2), peak closing velocity (mm/sec), open quotient, and vibratory stiffness (ratio of maximum velocity by maximum displacement) and closed quotient. The proposed research is significant in filling a gap in knowledge concerning the most effective methods for assessing vibratory function and identifying predisposing factors in children with hoarseness. The fundamental knowledge of vibratory function obtained from this work will directly translate to the clinic by producing meaningful findings and measures that can be applied to pediatric vocal health outcomes and will thus reduce the burden of illness and disability caused by voice disorders in children.